ValidationException: text content blocks must be non-empty when using Bedrock Runtime #15715

Description

Description

When using opencode with AWS Bedrock Runtime (InvokeModelWithResponseStream), a ValidationException is thrown with the message:

messages: text content blocks must be non-empty
This error occurs during normal conversation — no empty message was sent by the user. It appears opencode is generating a request that contains an empty text content block, which Bedrock rejects.

Error Message

InvokeModelWithResponseStream: operation error Bedrock Runtime: InvokeModelWithResponseStream,
https response error StatusCode: 400,
RequestID: 1864b9d1-6a4d-441b-a404-46e48820db57,
ValidationException: messages: text content blocks must be non-empty

Steps to Reproduce

1. Start a normal conversation session using opencode with AWS Bedrock as the provider
2. Send a non-empty message
3. Error occurs consistently on every request

Expected Behavior

Messages are sent to Bedrock API with valid, non-empty text content blocks.

Actual Behavior

Bedrock returns HTTP 400 with ValidationException: messages: text content blocks must be non-empty, suggesting opencode is including an empty text block in the API request body.

Environment

• Platform: macOS (darwin)
• Provider: AWS Bedrock Runtime
• Model: Claude Sonnet 4.6
• Provider: Custom Provider

Possible Cause

opencode may be including empty text content blocks (e.g. {"type": "text", "text": ""}) in the messages array when constructing the API request, possibly related to tool use results or message history serialization.

Plugins

No response

OpenCode version

1.2.15

Steps to reproduce

No response

Screenshot and/or share link

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Operating System

No response

Terminal

No response